Field of the Invention
This invention relates to methods and apparatus for conveyance of granular resin material, particularly granular plastic resin material, typically within facilities where plastic molding and/or plastic extrusion is performed.
Description of the Prior Art
In the plastics industry, it is common practice to have many molding machines and/or extruders, and many different granular plastic resins, and to use different granular plastic resins for different molding projects and/or extrusion projects. As a result, there is a need to be able to convey the resins to the correct molding machine or extruder.
As an example, a molding facility or an extruding facility may have ten material storage silos located outside of the facility with different types of granular plastic resin in each silo. In the molding or extrusion facility, there may be twenty molding machines or extruders. Clearly there is the need for a system to connect any one of the molding machines or extruders to any one of the granular resin material storage silos.
The most common practice is to fill a large box, conventionally referred to as a “Gaylord”, with resin material from one of the silos and to move the Gaylord by using a forklift truck to the desired molding machine or extruder. This is the crudest, most elementary approach. A slightly more sophisticated approach is to convey the granular resin material directly from the silos to the desired molding machine or extruder, with all of the granular plastic resin material passing through a common area where connections can be altered by hand as required. This is done by manually disconnecting and reconnecting conveying conduits, one conduit for each molding machine or extruder, with that conveying conduit connected to the desired silo so that the proper granular resin material can be delivered to a particular molding machine or extruder. This disconnecting and reconnecting of conveying lines is done by hand, much like an old-time telephone operator connecting one's call to the proper destination by plugging a cable into a socket corresponding to the recipient of the call. Manually disconnecting and reconnecting granular resin material conveying lines is labor-intensive and subject to error by the laborers making the connections.
A step up in sophistication from the manual connection of the conveying lines to the molding machines or extruders is to facilitate such connections automatically with computer control.
One approach using computer control is to employ a rotating material selection device, driven by a stepping motor, allowing a single machine to select from one of several granular resin material supply lines. For every molding machine or extruder, there is one such rotating device driven by a stepping motor.
Another approach is to use two rotating devices, one that rotates to select a molding machine or extruder while the second rotating device rotates to select the desired material. The two rotating devices are connected at their centers, much like a set of “Siamese twins.” In using this approach, any one of the molding machines or extruders can be selected to receive any of the materials stored in any of the storage silos at the facility. The granular resin material passes into a first one of the rotating devices, which is connected to the selected silo containing the proper granular resin material. This first device transfers the material to the second device as the two devices rotate. The second device has a selected molding machine or extruder destination and parses out the desired material to the correct molding machine or extruder.
No matter what the approach, whether it be manual or automated, to supplying granular plastic resin material to a molding machine or extruder, with such molding machines and extruders being collectively referred to herein as “process machines”, granular plastic resin material is furnished to the process machines via “material source lines” that run throughout the plant.